There's a difference between "design a system for me" and "recommend a system."
Mason: the first thing to consider is what sort of things you're going to need the system to do. It looks like you're going with a scifi combat game, a lot like Star Wars. The current Star Wars RPGs use a d20 system.
Actions have a difficulty. For example, 10 is about average (since it's right in the middle.) so if you roll 10 or more on a 20-sided die, you succeed. The roll or the difficulty can be modified by bonuses or penalties from stats and skills.